package com.zcp.flowlayoutdemo;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

import java.util.ArrayList;
import java.util.List;

import static android.view.View.MeasureSpec.getSize;

/**
 * Created by Administrator on 2017/3/31.
 */

public class FlowLayou extends ViewGroup {

    //存储所有的view,,一行一行的存储
    private List<List<View>> mAllViews = new ArrayList<>();
    //每一行的高度
    private List<Integer> mLineHeight = new ArrayList<>();

    //new一个控件
    public FlowLayou(Context context) {
        this(context, null);
    }


    //布局中写某个控件,没有写自定义控件
    public FlowLayou(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public FlowLayou(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        mAllViews.clear();
        mLineHeight.clear();
        //当前Viewgroup的宽度
        int width = getWidth();

        int lineWidth = 0;
        int lineHeight = 0;
        List<View> lineViews = new ArrayList<>();
        int cCount = getChildCount();
        for (int i = 0; i < cCount; i++) {
            View child = getChildAt(i);
            MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
            //子view占据的宽度
            int childWidth = child.getMeasuredWidth();
            int childHeight = child.getMeasuredHeight();

            //如果需要换行
            if (childWidth + lineWidth + lp.leftMargin + lp.rightMargin > width) {

                //记录lineHeight
                mLineHeight.add(lineHeight);

                //记录当前行的vIEWS
                mAllViews.add(lineViews);

                //重置行宽和行高
                lineWidth = 0;
                lineHeight = childHeight + lp.topMargin + lp.bottomMargin;
                lineViews = new ArrayList<>();
            }
            lineWidth += childWidth + lp.leftMargin + lp.rightMargin;
            lineHeight = Math.max(lineHeight, childHeight + lp.topMargin + lp.bottomMargin);
            lineViews.add(child);

        }

        //处理最后一行
        mLineHeight.add(lineHeight);
        mAllViews.add(lineViews);

        //设置子view的位置
        int left = 0;
        int top = 0;
        int lineNum = mAllViews.size();
        for (int i = 0; i < lineNum; i++) {
            //当前行的所有view
            lineViews = mAllViews.get(i);
            lineHeight = mLineHeight.get(i);
            for (int j = 0; j < lineViews.size(); j++) {
                View child = lineViews.get(j);

                //判断child的状态
                if (child.getVisibility() == View.GONE) {
                    continue;
                }
                MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
                int lc = left + lp.leftMargin;
                int tc = top + lp.topMargin;
                int rc = lc + child.getMeasuredWidth();
                int bc = tc + child.getMeasuredHeight();
                //为子view进行布局
                child.layout(lc, tc, rc, bc);
                left += child.getMeasuredWidth() + lp.leftMargin;
            }
            left = 0;
            top += lineHeight;
        }
    }


    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        //测量=测量模式+测量大小
        int sizeWidth = getSize(widthMeasureSpec);
        //宽度的测量模式
        int modeWidth = MeasureSpec.getMode(widthMeasureSpec);
        //因为布局文件中是fill_parent,对应的是exactly
        int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);
        int modeHeight = MeasureSpec.getMode(heightMeasureSpec);
        //如果写的是fill_parent/准确的精度值,在这里就不需要计算他的宽度和高度
       /*
       * 但如果写的是wrap_content的话,view的宽和高就需要计算
       * */
        int width = 0;
        int height = 0;

        //记录每一行的宽度和高度
        int lineWidth = 0;
        int lineHeight = 0;

        //得到内部元素的个数
        int cCount = getChildCount();

        for (int i = 0; i < cCount; i++) {
            View child = getChildAt(i);

            //测量子view的宽和高
            measureChild(child, widthMeasureSpec, heightMeasureSpec);
            //得到LayoutParams
            MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
            //子view占据的宽度
            int childWidth = child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
            //子view占据的高度
            int childHeight = child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;

            //换行
            if (lineWidth + childWidth > sizeWidth) {

                //对比得到最大的宽度
                width = Math.max(width, lineWidth);
                //重置lineWidth
                lineWidth = childWidth;
                //记录行高
                height += lineHeight;

                lineHeight = childHeight;
            } else//不换行
            {
                //叠加行宽
                lineWidth += childWidth;
                //得到当前行最大的高度
                lineHeight = Math.max(lineHeight, childHeight);
            }

            //最后一个控件
            if (i == cCount - 1) {
                width = Math.max(lineWidth, width);
                height += lineHeight;
            }

        }

        //wrap_content
        if (modeWidth == MeasureSpec.AT_MOST) {
            setMeasuredDimension(width, height);
        } else {
            setMeasuredDimension(sizeWidth, sizeHeight);
        }
        if (modeHeight == MeasureSpec.AT_MOST) {
            setMeasuredDimension(width, height);
        } else {
            setMeasuredDimension(sizeWidth, sizeHeight);
        }

    }

    //指明当前ViewGroup和LayoutParams之间的关系

    @Override
    public LayoutParams generateLayoutParams(AttributeSet attrs) {
        return new MarginLayoutParams(getContext(), attrs);
    }
}
